Sleep apnea is a potentially life-threatening breathing disorder characterized by brief interruptions of breathing during sleep. There are two types of sleep apnea: central and obstructive. Central sleep apnea, which is less common, occurs when the brain fails to send the appropriate signals to the breathing muscles to initiate respirations. Obstructive sleep apnea occurs when air cannot flow into or out of the person's nose or mouth although efforts to breathe continue. In a given night, the number of involuntary breathing pauses or “apneic events” may be as high as 20 to 60 or more per hour. Sleep apnea can also be characterized by choking sensations. The frequent interruptions of deep, restorative sleep often leads to excessive daytime sleepiness and may be associated with an early morning headache. Early recognition and treatment of sleep apnea is important because it may be associated with irregular heartbeat, high blood pressure, heart attack, and stroke.
Various forms of positive airway pressure during sleep can be an effective form of therapy for the apnea sufferer. Ventilation can be applied in the form of continuous positive airway pressure, in which positive pressure is maintained in the airway throughout the respiratory cycle; bi-level positive airway pressure system, in which positive pressure is maintained during inspiration but reduced during expiration; and intermittent (non-continuous) positive pressure, in which pressure is applied when an episode of apnea is sensed. In such procedures, a patient wears a mask over the nose during sleep, and pressure from an air blower forces air through the nasal passages. Typically, a thin flexible tube made of an inert material transports the air. The tube terminates in an opening that can be inserted into the patient's nostrils. A pair of smaller nasal insert tubes can protrude from the tube or the tube can split at a Y-junction into two smaller tubes, each smaller nasal insert tube carrying gas to one nostril, thereby increasing the fraction of inspired oxygen.
Conventional nasal tube systems do not provide a positive seal between the nasal insert tubes and the nostrils. Most nasal ventilation systems therefore include a mask that fits over the nose and is intended to provide a space of oxygen-enriched air for inhalation into the lungs for respiration. Such systems frequently suffer from air leaking out around the mask, creating an inability to assure ventilation in many patients. Additionally, most systems are usually very position dependent, whereby if the mask is moved slightly with respect to the facial contour or with respect to the nose, air leakage occurs. With such systems, the mask can become uncomfortable when not in position, thus requiring the patient to remain rather still in order to alleviate the discomfort and to maintain oxygen inspiration.